Marine biotoxins and harmful algae are a significant and expanding threat to human health and fisheries resources throughout the US. Five human illnesses are associated with toxic algae and consumption of seafood contaminated by harmful algae blooms (HAB) toxins: paralytic, neurotoxic, amnesic, and diarrhetic shellfish poisoning (called PSP, NSP, ASP, and DSP, respectively), and ciguatera fish poisoning (CFP). In addition to the adverse human health effects, whales, porpoises, seabirds, and other marine animals can become victims as well, accumulating algal toxins through the food chain by ingesting contaminated zooplankton or fish. Problems associated with harmful algal blooms have increased considerably in recent years, due in part to the simultaneous expansion of the fish-farming industry. Virtually every coastal state in the United States has reported recurring major blooms of harmful algae.
Optical devices are useful for analyzing optical changes in a sample that is found in a complex environment, such as the ocean. Such devices are particularly useful in identifying particular types of algae or other materials that fluoresce or absorb light. In general, either the absorbance or the fluorescence of a sample is measured and then interrogated to detect individual plant pigments. However, these approaches fail to discriminate a wide-range of plant pigments, missing critical information needed for the spectral characterization of water.
Leaf in U.S. Pat. No. 3,649,833 discloses a self-contained submersible fluorometer designed for the continuous in situ recording of concentrations of materials in an aqueous environment. The instrument can either be towed behind a moving boat or placed at rest in a flowing stream with the faired nose portion of the instrument facing the current. The pressure difference between an intake duct and an outlet duct causes water to flow through a transparent cuvette. A curved duct carries the water sample to and from the cuvette. A filter passes light from an excitation source which emits radiation at wavelengths which excite the sample material, whose concentration is to be detected, to fluoresce. As the material fluoresces, a filter that is selected to pass only those wavelengths of light from the desired fluorescent light to a photodetector. By continuously plotting the output of a potentiometer, vertical and horizontal profiles of material concentrations can be obtained for use in circulation and dilution studies. In particular, if the concentration of phytoplankton is to be determined, one need only replace the excitation filter with a filter that passes radiation over those wavelengths which excite chlorophyll to fluorescence. An emission filter is selected to pass those wavelengths characteristic of fluorescing chlorophyll. A photodetector is selected to be sensitive to all the wavelengths under consideration. That is, in making concentration measurements the photodetector is sensitive to the wavelengths emitted by the excitation lamp as well as the wavelengths which pass through the emission filter. The output from the photodetector passes through a bandpass filter-amplifier to produce an input to a synchronous detector. An integrator acts to integrate the output from the detector to produce a waveform. The problem with this approach is that the configuration of the device does not allow for the collection of data over a continuous range of wavelengths. Nor does it provide for the use of multiple excitation sources. Rather, the output from the photodetector corresponding to the light from the optical fiber increases in response to the detection of an increase in fluorescence of the sample material. As the intensity of light in the balancing path increases, the intensity difference in the two arms of the bridge decreases causing decay in the waveform. Hence the data collected is for a discrete wavelength rather than a continuous range of wavelengths.
Opti-Sciences, Inc. have disclosed a portable fluorometer and spectrometer on its website www.optisci.com/fsp2.htm. The device is capable of measuring fluorescence and absorbance in the same instrument. A standard configuration comes equipped with both a fluorometer and a spectrometer module. However, it also functions as a stand alone spectrometer or fluorometer. The instrument can also be equipped with application specific filters (up to 5 excitation and 6 emissions) for multi-fluorescence analysis. This device differs from that of the present invention because it is limited to testing at a discrete wavelength rather than over a continuous range of wavelengths. Nor does the device allow for multiple excitation sources.
An object of the present invention is to provide a device and method for measuring optical properties in a sample where the device generates a continuous fluorescence emission spectrum.
Another object of the present invention is to provide a device and method for measuring optical properties over a range of wavelengths.
Another object of the present invention is to provide a device that is capable of detecting fluorescence, absorbance, or fluorescence and absorbance simultaneously.